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OrientedCylinder

Repository source: OrientedCylinder

Description

This example illustrates how to create and display a cylinder that passes through two points.

It demonstrates two different ways to apply the transform:

  1. Use vtkTransformPolyDataFilter to create a new transformed polydata. This method is useful if the transformed polydata is needed later in the pipeline, e.g. vtkGlyph3DFilter.

  2. Apply the transform directly to the actor using vtkProp3D's SetUserMatrix. No new data is produced.

Switch between the two methods by #defining USER_MATRIX or leaving out the #define.

See also

Compare this example with OrientedArrow. The transform is different because the cylinder height direction is along the y-axis and the arrow height is along the x axis.

Other languages

See (Python), (PythonicAPI), (Java)

Question

If you have a question about this example, please use the VTK Discourse Forum

Code

OrientedCylinder.cxx

#include <vtkActor.h>
#include <vtkCylinderSource.h>
#include <vtkMath.h>
#include <vtkMinimalStandardRandomSequence.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkSphereSource.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>

#include <array>

#define USER_MATRIX

int main(int, char*[])
{
  vtkNew<vtkNamedColors> colors;

  // Set the background color.
  std::array<unsigned char, 4> bkg{{26, 51, 77, 255}};
  colors->SetColor("BkgColor", bkg.data());

  // Create a cylinder.
  // Cylinder height vector is (0,1,0).
  // Cylinder center is in the middle of the cylinder
  vtkNew<vtkCylinderSource> cylinderSource;
  cylinderSource->SetResolution(15);

  // Generate a random start and end point
  double startPoint[3];
  double endPoint[3];
  vtkNew<vtkMinimalStandardRandomSequence> rng;
  rng->SetSeed(8775070); // For testing.
  for (auto i = 0; i < 3; ++i)
  {
    rng->Next();
    startPoint[i] = rng->GetRangeValue(-10, 10);
    rng->Next();
    endPoint[i] = rng->GetRangeValue(-10, 10);
  }

  // Compute a basis
  double normalizedX[3];
  double normalizedY[3];
  double normalizedZ[3];

  // The X axis is a vector from start to end
  vtkMath::Subtract(endPoint, startPoint, normalizedX);
  double length = vtkMath::Norm(normalizedX);
  vtkMath::Normalize(normalizedX);

  // The Z axis is an arbitrary vector cross X
  double arbitrary[3];
  for (auto i = 0; i < 3; ++i)
  {
    rng->Next();
    arbitrary[i] = rng->GetRangeValue(-10, 10);
  }
  vtkMath::Cross(normalizedX, arbitrary, normalizedZ);
  vtkMath::Normalize(normalizedZ);

  // The Y axis is Z cross X
  vtkMath::Cross(normalizedZ, normalizedX, normalizedY);
  vtkNew<vtkMatrix4x4> matrix;

  // Create the direction cosine matrix
  matrix->Identity();
  for (unsigned int i = 0; i < 3; i++)
  {
    matrix->SetElement(i, 0, normalizedX[i]);
    matrix->SetElement(i, 1, normalizedY[i]);
    matrix->SetElement(i, 2, normalizedZ[i]);
  }

  // Apply the transforms
  vtkNew<vtkTransform> transform;
  transform->Translate(startPoint);   // translate to starting point
  transform->Concatenate(matrix);     // apply direction cosines
  transform->RotateZ(-90.0);          // align cylinder to x axis
  transform->Scale(1.0, length, 1.0); // scale along the height vector
  transform->Translate(0, .5, 0);     // translate to start of cylinder

  // Transform the polydata
  vtkNew<vtkTransformPolyDataFilter> transformPD;
  transformPD->SetTransform(transform);
  transformPD->SetInputConnection(cylinderSource->GetOutputPort());

  // Create a mapper and actor for the cylinder
  vtkNew<vtkPolyDataMapper> mapper;
  vtkNew<vtkActor> actor;
#ifdef USER_MATRIX
  mapper->SetInputConnection(cylinderSource->GetOutputPort());
  actor->SetUserMatrix(transform->GetMatrix());
#else
  mapper->SetInputConnection(transformPD->GetOutputPort());
#endif
  actor->SetMapper(mapper);
  actor->GetProperty()->SetColor(colors->GetColor3d("Cyan").GetData());

  // Create spheres for start and end point
  vtkNew<vtkSphereSource> sphereStartSource;
  sphereStartSource->SetCenter(startPoint);
  sphereStartSource->SetRadius(0.8);
  vtkNew<vtkPolyDataMapper> sphereStartMapper;
  sphereStartMapper->SetInputConnection(sphereStartSource->GetOutputPort());
  vtkNew<vtkActor> sphereStart;
  sphereStart->SetMapper(sphereStartMapper);
  sphereStart->GetProperty()->SetColor(colors->GetColor3d("Yellow").GetData());

  vtkNew<vtkSphereSource> sphereEndSource;
  sphereEndSource->SetCenter(endPoint);
  sphereEndSource->SetRadius(0.8);
  vtkNew<vtkPolyDataMapper> sphereEndMapper;
  sphereEndMapper->SetInputConnection(sphereEndSource->GetOutputPort());
  vtkNew<vtkActor> sphereEnd;
  sphereEnd->SetMapper(sphereEndMapper);
  sphereEnd->GetProperty()->SetColor(colors->GetColor3d("Magenta").GetData());

  // Create a renderer, render window, and interactor
  vtkNew<vtkRenderer> renderer;
  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->AddRenderer(renderer);
  renderWindow->SetWindowName("OrientedCylinder");
  vtkNew<vtkRenderWindowInteractor> renderWindowInteractor;
  renderWindowInteractor->SetRenderWindow(renderWindow);

  // Add the actor to the scene
  renderer->AddActor(actor);
  renderer->AddActor(sphereStart);
  renderer->AddActor(sphereEnd);
  renderer->SetBackground(colors->GetColor3d("BkgColor").GetData());

  // Render and interact
  renderWindow->Render();
  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(OrientedCylinder)

find_package(VTK COMPONENTS 
  CommonColor
  CommonCore
  CommonTransforms
  FiltersGeneral
  FiltersSources
  InteractionStyle
  RenderingContextOpenGL2
  RenderingCore
  RenderingFreeType
  RenderingGL2PSOpenGL2
  RenderingOpenGL2
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "OrientedCylinder: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(OrientedCylinder MACOSX_BUNDLE OrientedCylinder.cxx )
  target_link_libraries(OrientedCylinder PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS OrientedCylinder
  MODULES ${VTK_LIBRARIES}
)

Download and Build OrientedCylinder

Click here to download OrientedCylinder and its CMakeLists.txt file. Once the tarball OrientedCylinder.tar has been downloaded and extracted,

cd OrientedCylinder/build

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

make

and run it:

./OrientedCylinder

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.